Applications that use Ehcache can be expected to use large heaps. Some Ehcache applications have heap sizes greater than 6 GB. Ehcache works well at this scale. However, large heaps or long held objects, which is what a cache is composed of, can place strain on the default Garbage Collector (GC). With Ehcache 2.3 and higher, this problem can be solved with BigMemory Go, an in-memory data management product, which provides an additional store outside of the heap. For more information, see the BigMemory Go product documentation.

A full garbage collection event pauses all threads in the JVM. Nothing happens during the pause. If this pause takes more than a few seconds, it will become noticeable.

The clearest way to see if this is happening is to run jstat. The following command will produce a log of garbage collection statistics, updated every ten seconds.

The thing to watch for is the Full Garbage Collection Time. The difference between the total time for each reading is the amount of time the system was paused. A jump of more than a few seconds will not be acceptable in most application contexts.